The proposed study is a double-masked, controlled, clinical trial to assess the effect of corticosteroids on the natural history of Graves' ophthalmology. A total of two hundred patients who are determined by quantitative clinical and diagnostic methods to be at-risk for the development of optic neuropathy will be recruited and followed for up to two years. The determination of risk is made by clinical examination, computerized tomographic scanning, and eye movement recording, according to procedures developed from previous work. Each patient will be randomized into a corticosteroid or placebo group and treated for a period of one out of every four months. Before and after each treatment period, clinical and motility evaluations will be performed. If deterioration is suspected, and confirmed by computed tomography, or if the optic nerve is compromised, then treatment failure will have occurred. Differences between the two groups will be evaluated by life table analysis and Cox regression. The goal of the initial grant was to form a better clinical classification of Graves' ophthalmopathy so that the disabling complications could be prevented or minimized by appropriate application of therapeutic interventions. Therefore, the proposed clinical trial represents a logical extension of past work.